As mentioned in your question, you'll be hard pressed to find hard numbers on the failures of totalitarian societies. So in a way, your question can't be answered concretely but we can find out if such a political failure is possible by analyzing each policy and reviewing what academia and historians have said.
The estimates vary wildly from 18 million (1) to 45 million (2) deaths, around 2-8% of the estimated 670 million inhabitants, died from mistreatment or starvation.
Policy: Four Pests Campaign
In 1958 Mao initiated a campaign to eradicate 4 pests (mosquitoes, flies, rats, and sparrows).
The masses of China were mobilized to eradicate the birds, and
citizens took to banging pots and pans or beating drums to scare the
birds from landing, forcing them to fly until they fell from the sky
in exhaustion. Sparrow nests were torn down, eggs were broken, and
nestlings were killed. By 1960, Chinese leaders realized that sparrows
ate a large amount of insects, as well as grains. Rather than
being increased, rice yields after the campaign were substantially
decreased
(3)
This problem was exacerbated by a devastating locust swarm, which was
caused when their natural predators were killed as part of the Great
Sparrow Campaign. Although actual harvests were reduced, local
officials, under tremendous pressure from central authorities to
report record harvests in response to the innovations, competed with
each other to announce increasingly exaggerated results. These were
used as a basis for determining the amount of grain to be taken by the
State to supply the towns and cities, and to export. This left barely
enough for the peasants, and in some areas, starvation set in.
(4)
Policy: Industrialisation
During this time 21 million people were taken out of agriculture. Resulting in major stress on China's food-rationing system, which led to increased and unsustainable demands on rural food production. (5)
Policy: Backyard Furnaces
Mao encouraged the establishment of small backyard steel furnaces in every commune and in each urban neighborhood...huge efforts on the part of peasants and other workers were made to produce steel out of scrap metal. To fuel the furnaces the local environment was denuded of trees and wood taken from the doors and furniture of peasants' houses. Pots, pans, and other metal artifacts were requisitioned to supply the "scrap" for the furnaces so that the wildly optimistic production targets could be met. Many of the male agricultural workers were diverted from the harvest to help the iron production as were the workers at many factories, schools and even hospitals. (6)
Policy: Irrigation Works
Trying to boost agricultural productivity, Mao, invested massive human resources in poorly planned water works. This resulted in the diversion and often death of thousands of agricultural workers.
Mao was well aware of the human cost of these water-conservancy campaigns. In early 1958, while listening to a report on irrigation in Jiangsu, he mentioned that:
"Wu Zhipu claims he can move 30 billion cubic metres; I think 30,000
people will die. Zeng Xisheng has said that he will move 20 billion
cubic metres, and I think that 20,000 people will die. Weiqing only
promises 600 million cubic metres, maybe nobody will die."
(7)
Policy: Crop Experimentation
On the communes, a number of radical and controversial agricultural innovations were promoted at the behest of Mao. The policies included close cropping, whereby seeds were sown far more densely than normal on the incorrect assumption that seeds of the same class would not compete with each other. Deep plowing (up to 2 m deep) was encouraged on the mistaken belief that this would yield plants with extra large root systems. Moderately productive land was left unplanted with the belief that concentrating manure and effort on the most fertile land would lead to large per-acre productivity gains. Altogether, these untested innovations generally led to decreases in grain production rather than increases.
(8)
Policy: Export and Food Aid
During the period of the Great Leap Forward, China continued to be a net exporter of grain, despite the widespread famine experienced in the countryside, as Mao sought to maintain face and convince the outside world of the success of his plans. Foreign aid was refused. When the Japanese foreign minister told his Chinese counterpart Chen Yi of an offer of 100,000 tonnes of wheat to be shipped out of public view, he was rebuffed. (9)
Conclusion
The Great Leap Forward was a series of political blunders that either exacerbated or caused the "worst famine in the history of the world" (10). The exact figures of the dead will never be known, but with the decimation of the agricultural industry, mistreatment of the rural workforce, rejection of food aid and continued export of grain during a time of widespread famine, it would be entirely possible that 2-8% of the population may starve.
Despite the risks to their careers, some Communist Party members openly laid blame for the disaster at the feet of the Party leadership. Liu Shaoqi made a speech in 1962 at Seven Thousand Cadres Conference criticizing that "The economic disaster was 30% fault of nature, 70% human error." (11)
- Gráda, Cormac Ó (2011). Great Leap into Famine. UCD Centre For Economic Research Working Paper Series. p. 9
- Dikötter, Frank. Mao's Great Famine: The History of China's Most Devastating Catastrophe, 1958-62. Walker & Company, 2010 p. 12 & 333
- Shapiro, Judith Rae (2001). Mao's War Against Nature: Politics and the Environment in Revolutionary China. Cambridge University Press.
- http://en.wikipedia.org/wiki/Great_Leap_Forward
- Lardy and Fairbank (1987)
- Cook, Ian G.; Geoffrey Murray (2001). China's Third Revolution: Tensions in the Transition Towards a Post-Communist China.
- The memoirs of Jiang Weiqing Jiangsu renmin chubanshe. p.421.
- Shenfan: The Continuing Revolution in a Chinese Village.
- Dikötter, Frank (1991). pp.114-115.
- Ashton, Hill, Piazza, and Zeitz (1984). Famine in China, 1958-61. Population and Development Review, Vol. 10, No. 4 (Dec., 1984). p.614
- Twentieth Century China: Third Volume. Beijing, 1994. p.430